MLAB 2401: Clinical Chemistry
Keri Brophy-Martinez
Liver Anatomy and Physiology
Where is the Liver?
• Upper right quadrant,
beneath the diaphragm
• Largest internal organ
• Weighs ~ 1500 grams
Anatomy of the Liver
• Consists of 2 lobes divided by falciform
ligament
• There is no known difference between the
lobes
Liver
• Vascular organ
– Hepatic artery
• Supplies O2 rich blood
from heart to liver
• Provides 20-30% of blood
supply to liver
– Portal vein
• Supplies nutrient rich
blood from the digestive
tract
• Provides 70-80% of blood
to liver
From
Aorta
From GI tract
Microscopic Anatomy of the Liver
• Lobules make up the
liver
– 6-sided structure
– Central vein with portal
triads at each corner
– Triad contains a hepatic
artery, portal vein and
bile duct surrounded by
connective tissue
– Function in metabolic
and excretory actions
Microscopic Anatomy of Liver
• Cell types
– Hepatocytes
• 70% of volume of liver
• Regenerative
• Perform major functions
of liver
– Kupffer cells
• Macrophages acting as
phagocytes
Biochemical Function of the Liver
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•
•
•
•
Excretion/Secretion
Synthesis
Detoxification
Storage
Immunologic
Excretory System
• Excretion of bile acids,
cholesterol, bilirubin
• Begins at the bile
canaliculi, enters
hepatic ducts, then to
common hepatic & bile
duct
Excretion/Secretion
• Liver processes and excretes
– Bile
• Water, electrolytes, phospholipids, bile salts or acids,
bile pigments, cholesterol , heme waste products, and
other substances from blood
• 3L produced/day
• 1L excreted/day
• Functions
• Bile acids needed for fat absorption
• Mechanism to remove cholesterol and waste
• Bilirubin is the principal pigment in bile
Bilirubin Metabolism
Metabolism of Bilirubin
• Around 126 days, RBCs are phagocytized and hgb released
• Hgb broken down into:
– Heme
• Converted to bilirubin
– Globin
• Broken into amino acids and recycled
– Iron
• Bound by transferrin and returned to iron stores in the
liver or bone marrow
Metabolism of Bilirubin
• Bilirubin
– Bound by albumin and taken to liver (unconjugated or indirect
bilirubin)
• Water insoluble
• Can not be removed from body
• Once at the liver, unconjugated bilirubin flows into sinusoidal tissue and
albumin releases it
• Ligandin, picks up the unconjugated bilirubin and presents it to glucuronic
acid
• In the liver it becomes conjugated with the help of UDP-glucuronyl
transferase
– Water soluble
– Combines with gallbladder secretions and expelled into intestines
Metabolism of Bilirubin
• Intestinal bacteria degrade conjugated bilirubin to form
urobilinogen
– 80% of urobilinogen formed is oxidized to stercobilin and
excreted in feces, giving stool the brown color
– 20% of urobilinogen formed
• Absorbed by extrahepatic circulation to be recycled
through liver and re-excreted
• Enters systemic circulation to be filtered by kidney and
excreted in urine
Synthesis
• Synthesize many biological compounds
– Carbohydrates
• Metabolism important
– Uses glucose for its own cellular energy
– Circulates glucose to peripheral tissue
– Stores glucose as glycogen
• Major player in maintaining stable glucose
concentration due to glycogenesis, glycogenolysis and
gluconeogenesis
Synthesis
– Lipids
• Liver gathers free fatty acids from diet and breaks them
down to Acetyl- CoA to form triglycerides,
phospholipids or cholesterol
• Converts insoluble lipids to soluble forms
• 70% of cholesterol produced by the liver
– Proteins
• Almost all proteins made in the liver
• Exceptions are immunoglobulins and hgb
Detoxification
• Liver serves as a gatekeeper between the circulation and
absorbed substances
– First pass: every substance absorbed in GI tract passes
through liver
• Detoxification includes drugs and poisons, and metabolic
products like ammonia, alcohol, and bilirubin
• 3 mechanisms
– Binds material reversibly to inactivate
– Chemically modify compound for excretion
– Drug metabolizer for detox of drugs and poisons
Storage
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•
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Glycogen
Vitamins
Iron
Blood
Immunologic
• Phagocytosis of bacteria
• IgA secretion
References
• Biofortified. (2012). Retrieved from
http://www.biofortified.org/2010/03/glowing-phagocytosis/
• Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry:
Techniques, principles, Correlations. Baltimore: Wolters
Kluwer Lippincott Williams & Wilkins.
• http://www.livercancer.com/liver_anatomy.html
• Sunheimer, R., & Graves, L. (2010). Clinical Laboratory
Chemistry. Upper Saddle River: Pearson .